The discovery of p53 in 1979 marks the beginning of a most fascinating era of modern cancer research and molecular biology, an era that is still in full swing and does not show any signs of ending in the foreseeable future. p53 has emerged as a key tumor suppressor and important target for novel cancer therapy. For around 10 years, p53 was considered an oncogene with somewhat unusual features. However, a major paradigm shift occurred around 1988-89 when exciting new findings demonstrated that normal (wild type) p53 could inhibit transformation of cells in culture and that the p53 gene was mutated in a large fraction of human tumors. In fact, p53 appeared to be the most frequently mutated gene in cancer cells. Subsequent work during the 1990s showed that p53 was a transcription factor that regulates many other genes, and that p53 can trigger apoptosis, the suicide program of the cell. This book, written by world-leading p53 researchers including many of those who have shaped the field over the past 25 years, provides unique insights into the progress of the p53 field and the prospects for better cancer diagnosis and therapy in the future. It should be of interest to everybody working in cancer research, clinical oncology, and molecular biology, and indeed to anybody interested in science, medicine, as well as in recent developments of the ideas and concepts of the molecular biology of cancer.